This invention is directed to star and access couplers for multimode optical fibers and waveguides and more particularly to couplers for minibundles, multichannel fiber cable, and planar single-fiber lines.
It is well known in the art that optical communication systems have been formed by use of optical waveguides in the form of bundles of multimode fibers (more than 18 fibers per bundle). Optical couplers have been provided which will direct optical radiation into and from the above. The present state of the art involves multichannel fiber cable with a small number of fibers as well as single fiber cable. The prior-art star and access couplers for multiterminal communication systems are not suitable for single fiber systems because they are designed for systems where each individual fiber is not important. These fibers are not individually available for inspection and because the input and output fibers are used in bundles, there is a large packing fraction loss between the fibers and their couplers. Further, prior-art couplers for multimode fibers are cylindrical and of such a diameter as to include the fibers and the low-index cladding.